How does niri msg outputs determine transform?

[fstanis]

I have a laptop that by default has the screen rotated (1200x1920 is the native resolution), so I added video=DSI-1:panel_orientation=right to my kernel cmdline to correct this.

However, this has a strange side-effect: niri msg outputs shows Transform: 270° counter-clockwise by default. If I try to actually apply niri msg output DSI-1 transform 270, this actually rotates the screen and niri msg outputs shows Transform: 180°.

While niri msg outputs seems to actually be correct, taking into account the kernel-level rotation, I'm curious how it does this? I was creating a small script that persists the current state of niri msg outputs to a .kdl file but this ended up being a bad idea since every run would rotate the screen.

[YaLTeR]

Not sure how to best handle this. We might need to exclude the transform based on panel orientation from niri msg outputs. Need to see how Mutter and GNOME Settings behaves.

[fstanis]

Perhaps we can display both in msg outputs, e.g.

Transform (session): normal
Transform (actual): 270° counter-clockwise

Or at least having both in --json output would help when it comes to tool automation. Or if you know an easy way I could derive this (i.e. reverse what msg outputs does), that'd be super useful.